Vibrations induced Doppler Spectrum for Millimetre Wave Vehicular Applications

The Implementation of millimetre waves (mmWave) frequencies in 5G and Beyond communication systems brings to light many propagation challenges concerning preserving the high directivity between the base station and a receiver’s antenna on a vehicle. The antenna depointing occurred because of the vibrations resulting from a vehicle’s suspension variation, causes changes to the phase of the received signal. This results in an additional modulation that needs to be considered by a system designer developing the Radio Frequency hardware. Therefore, this research investigates the influence of vertically vibrated antenna on the observed Doppler power Spectrum considering horizontal (H) or vertical (V) antenna’s polarisation. A laboratory model has been developed to perform a vertical vibration at either the transmitter or the receiver side. The University of Bristol (UoB) channel sounder working with 26GHz has been used to perform measurements and investigate the impact of the 3cm antenna’s vertical displacements on the observed Doppler Power Spectrum. The measured channel impulse response (CIR) was post-processed to compute the Doppler power spectrum for a bandwidth frequency of 1GHz. The results showed around 10dBm Doppler power spectrum difference between H and V polarised horn antenna. Moreover, a high Doppler power spectrum of around 2dBm is spotted if Rx vibrates rather than Tx one.